1. Field of the Invention
The present invention relates to lever operation devices suitable for use as, for example, turn signal switch devices or wiper switch devices of automobiles. More specifically, the present invention relates to a lever operation device capable of outputting various operation signals when operation members, such as a rotating knob, arranged on the outer periphery of an operation lever are operated.
2. Description of the Related Art
Lever operation devices used as turn signal switch devices or wiper switch devices of automobiles generally include a columnar operation lever that projects from a housing fixed to, for example, a steering column The operation lever can be pivoted along two operation planes that are substantially orthogonal to each other. The operation lever is selectively operated along the individual operation planes, and a plurality of types of operation signals are output in accordance with the direction in which the operation lever is operated. Lever operation devices having operation members, such as a rotating knob, on the outer periphery of the operation lever are also known. Such a lever operation device outputs operation signals corresponding to operations of the operation members (for example, rotation of the rotating knob).
Recently, lever operation devices having a long-life detection mechanism capable of detecting the operation position of the rotating knob have been proposed (see, for example, Japanese Unexamined Patent Application Publication No. 2009-224057). Such a lever operation device according to the related art includes a driven member driven by the rotating knob, a permanent magnet fixed to the driven member, and a magnetic sensor mounted on a circuit board in an inner space of the operation lever. The driven member and the permanent magnet are moved or rotated together in response to the rotation of the rotating knob. Accordingly, a variation in magnetic field caused by the movement or rotation of the permanent magnet may be detected by the magnetic sensor. Therefore, continuity failures due to abrasion with time, oxidation, etc., which have been a problem in detection mechanisms having a structure in which a slider is caused to slide along a conductive pattern, can be suppressed. Accordingly, the operation opposition of the rotating knob can be reliably detected for a long time.
The lever operation device according to Japanese Unexamined Patent Application Publication No. 2009-224057 includes a magnetic detection mechanism in which the permanent magnet is moved or rotated in response to the rotation of the rotating knob. However, when the permanent magnet is moved along an arc or a straight line in response to the rotation of the permanent magnet, the permanent magnet cannot be rotated while the permanent magnet is near the magnetic sensor. In the case where the permanent magnet is configured to rotate while the permanent magnet is near the magnetic sensor, a ring gear portion that rotates together with the rotating knob and a driving gear externally mounted on a shaft portion of a holder placed in the operation lever are arranged so as to directly mesh with each other. Since there is a limit to how small the diameter of the driving gear can be set with respect to the diameter of the ring gear portion, the speed-increasing ratio of the driving gear to which the permanent magnet is fixed cannot be set to a large value. Therefore, it is difficult to rotate the permanent magnet by a large amount in response to the rotation of the rotating knob. Therefore, in the structure of the related art, there has been a problem in that it is difficult to accurately detect the operation position of the rotating knob at a high resolution and the detection resolution is low.